The air in a room in a home or other building becomes stale when the air remains stagnant. Air is often stagnant during periods when the ventilation is idle. Such idle periods occur when the desired temperature is achieved and heating or cooling is no longer required. This is particularly true in a home ventilation system where the blower only operates when heating or cooling is needed to conserve energy. In many areas during autumn and spring, heating or cooling is not needed at all in the home or needed for only brief periods of time contributing to stale air. Where the blower operation is adequate to keep the air circulating and filtered, the air can still be less than pleasant because of odors from cooking, smoking or other activities. Without the benefit of adequate air filtration, odors from cooking and smoking can settle on drapes and carpets making the undesirable odors ever present.
Sometimes it is desirable to create an aroma in a room for a special occasion or for a particular season. For example, during the winter holiday season, a pine fragrance enhances the holiday tree and decorations making for a more festive occasion. Similarly, a nutmeg or spice aroma enhances the thanksgiving holiday season because the aroma hints of pumpkin pie and other good things to eat. It is now recognized that certain fragrances invoke or enhance certain moods or reactions in people. The use of fragrances to create or alter moods is known as aroma therapy. Home aroma therapy has heretofore used scented candles or hand held sprays. Both require user intervention requiring the user to intentionally start the therapy which is not realistic when the person is not in a good mood. Also, candles could present a burn or fire hazard to an irritable person. It is desirable to have a fragrance dispenser that operates automatically to dispense fragrance for aroma therapy and special occasions and situations. It is also desirable to have a single fragrance dispenser that can deliver more than one fragrance.
Fragrance dispensers are now available in a variety of configurations, but are limited in their effectiveness because the fragrance substance used to impart the aroma is not present in its most concentrated form; that is, these devices do not use the concentrated fragrance oils as they come from the manufacture. The oils are diluted with alcohol or mixed with a binder to slow evaporation. When the delivery device is a canister with a spray nozzle, the fragrance oil is diluted with alcohol so that a spray develops without clogging the nozzle. When the delivery device is a plug-in unit, the fragrance oil is mixed with a binder so that fragrance is only released when the electric current is applied. It is desirable to have a delivery device that uses the fragrance substance in its concentrated form for maximum effectiveness and longest life per unit volume of fragrance substance.
Another problem with conventional delivery devices is that the strength of the aroma is not constant over the life of the fragrance substance. A fragrance substance mixed with other materials does not always remain uniformly mixed causing uneven amount of fragrance to be emitted. Also, the evaporation rates of the fragrance substance and binder may differ causing uneven fragrance to be emitted. This is particularly true as the substance is depleted causing the aroma strength to weaken as the substance is consumed. Accordingly, it will be appreciated that it would be highly desirable to have an aroma delivery system that provides constant aroma strength as the fragrance substance is consumed.